(a) Field of the Invention
This invention relates to stable liquid disinfectant laundry detergent concentrates having valuable anti-soil redeposition properties and to the method of preventing soil redeposition in the washing of textile fabrics by the use thereof.
(b) Information Disclosure Statement
It is well known that certain anti-soil redeposition agents, such as sodium carboxymethylcellulose, can be used in solid, powdered laundry detergents in order to prevent redeposition of soil and thus to prevent graying during the wash cycle. It is also known to use so-called optical brighteners which essentially "mask" the gray coloration produced as a result of soil redeposition. However, the latter approach to fabric brightening is unsatisfactory, because it fails to remove the source of the problem, and furthermore conventional anti-redeposition agents, such as sodium carboxymethylcellulose, cannot be used in liquid laundry detergents, because they tend to separate out of the liquid formulation and thus lose their effectiveness.
Thus Jones et al. Canadian Pat. No. 1,137,381 discloses solid laundry detergent compositions for prevention of static build-up on textile fabrics and for softening the fabrics laundered therewith. The compositions are composed of an anionic surfactant, a non-ionic surfactant and an anti-static agent of the general formula [R.sub.1 R.sub.2 R.sub.3 R.sub.4 N].sup.+ Y.sup.- where at least one, but no more than two, of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 can be a C.sub.16 -C.sub.22 aliphatic group, the remainder of the R.sub.1, R.sub.2, R.sub.3 and R.sub.4 groups being C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 hydroxy-lower-alkyl and "cyclic structures in which the nitrogen atom forms part of the ring" and Y.sup.- is an anion. The ratio of the anionic to the non-anionic surfactants is 2:1 to 15:1, preferably 2:1 to 10:1, and most preferably 3:1 to 6:1. The quaternary ammonium salt is intended to impart anti-static properties to the compositions, and no mention is made by the patentee of any germicidal property resident in the combination. Furthermore, the question of preventing soil redeposition is not addressed by the reference, and thus the reference provides no guidance as to how to overcome that problem in laundry detergents. Moreover the patent does not disclose the use of an alkyl-alkoxy carboxylate as an anionic surfactant, and no mention is made of the adaptation of the formulation to liquid laundry detergents.
Wright U.S. Pat. No. 4,272,395 discloses liquid dishwashing compositions having germicidal properties while retaining good foaming behavior. The compositions are composed of 50-95 parts by weight of a germicidal cationic surfactant of the quaternary ammonium salt type and from 5-50 parts by weight of a co-surfactant of the alkylsulfonate, sulphate, phosphate or carboxylic acid type having from 3 to 8 carbon atoms in the hydrophobic alkyl group and from 0 to 20 parts by weight of a non-ionic surfactant of the mono- or diethanolamide or ethoxylated or propoxylated primary or secondary C.sub.8 -C.sub.16 alkanol type containing from 1 to 4 ethyleneoxy or propyleneoxy units per molecule. Being directed to dishwashing detergents, the reference manifestly does not address the problem of soil redeposition in laundry detergents.
Beeks U.S. Pat. No. 4,264,457 discloses laundry detergent/fabric softener/anti-static compositions composed of 3-35 weight percent of a non-ionic surfactant formed from ethylene oxide and a hydrophobic organic compound; 3-30 weight percent of a mono C.sub.8 -C.sub.22 long chain aliphatic cationic surfactant of the quaternary ammonium type and an anionic surfactant mixture consisting of a C.sub.4 -C.sub.10 alkylsulfate and a C.sub.12 -C.sub.22 alcohol ethoxylated ether sulfate or carboxylate having from 1 to about 15 moles of ethylene oxide per molecule and where the anionic surfactants are present in a ratio of 1:5 to 5:1 and the cationic:anionic surfactant mole ratio is 0.8:1 to 10:1. The patentee teaches that combinations of di-long chain quaternary ammonium surfactants in liquid detergents are unstable and separate into two phases and also that combinations of anionic and cationic detergents often produce precipitates. The nature of the four or five ingredients, and their relative amounts, are both critical, and the anionic surfactant serves principally to assist in suspending or dissolving the cationic-anionic complex that would otherwise form and separate out. The patentee does not address either the question of imparting germicidal properties to the composition or of preventing soil redeposition. On the contrary, the patentee is primarily concerned with solving the problem of precipitation of the anionic-cationic complex.